Redundancy circuit in semiconductor memory device

ABSTRACT

A redundancy circuit in a semiconductor memory device comprises a fuse set controller configured to output a redundancy enable signal enabled according to applied address signals; a redundant selector; a spare redundant selector; and a spare fuse controller configured to be controlled by the redundancy enable signal, and to output a selection control signal that selects at least one of the redundant selector and the spare redundant selector in accordance with an internal fuse option.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application contains subject matter related to Korean patentapplication No. 2005-36227, filed in the Korean Patent Office on Apr.29, 2005, the entire contents of which being incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device; and, moreparticularly, to a redundancy circuit in a semiconductor memory device.

In general, a semiconductor memory device undergoes a predetermined testin a wafer state so that undesired cells, word lines, bit lines or thelike having errors or defects therein are sort out. Furthermore, thesame test is also carried out for a redundancy circuit in order to findout defects. As is well known, the redundancy cell array is required inthe semiconductor memory device in order for a cell in the redundancycell array to perform a normal operation in place of an arbitrary cellin a normal cell array, if the arbitrary cell in the normal cell arraycannot perform its function for any reason.

FIG. 1 is a block diagram setting forth a prior art redundancy circuitand FIG. 2 is a timing diagram representing operation of the prior artredundancy circuit.

Herein, a fuse set controller 110 is configured with a fuse set forstoring a set of address signals and a controller for controlling theset of address signals.

Referring to FIGS. 1 and 2, in order to test for finding out defects ina predetermined redundancy circuit, a redundancy test signal RED_TEST isapplied to the fuse set controller 110 so that the redundancy circuitgoes into a test mode after a T2 period. The fuse set controller 110outputs a redundancy enable signal REDEN<0:3> of logic high levelaccording to a predetermined combination of applied address signalsADDRESS. Afterwards, when a selection control signal SEL_CTRL is appliedto a redundant selector 120 while the redundancy enable signalREDEN<0:3> is applied thereto, the redundant selector 120 outputs aredundant selection signal RED_SEL<0:3>. Herein, a T1 period correspondsto an operation time for setting the redundancy circuit and a periodbetween the T1 and the T2 is correspondent to a normal operation time ofthe redundancy circuit.

However, since one redundant substitution unit is arranged in one fuseset according to the prior art redundancy circuit, there is a drawbackthat it is impossible to utilize the fuse set if there is any defect inthe redundant substitution unit. Meanwhile, although semiconductormemory devices have become smaller as process technology has become moreenhanced, an occupation area of the fuse set in the device is stillrelatively large so that it is difficult to implement a highlyintegrated device, wherein another problem arises.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a redundancy circuit in which aplurality of redundant substitution units are arranged in one fuse setfor enhancing use efficiency of a fuse set.

In accordance with an embodiment of the present invention, a redundancycircuit of a semiconductor memory device comprises: a fuse setcontroller for outputting a redundancy enable signal, such redundancyenable signal enabled according to applied address signals; a redundantselector; a spare redundant selector; and a spare fuse controller whichis controlled by the redundancy enable signal and configured to output aselection control signal that selects at least one of the redundantselector and the spare redundant selector in accordance with an internalfuse option.

In accordance with another embodiment of the present invention, aredundancy circuit of a semiconductor memory device comprises: a fuseset controller for outputting a redundancy enable signal, such fuse setcontroller enabled according to applied address signals; a redundantselector for outputting a redundant selection signal; a spare redundantselector for outputting a spare redundant selection signal; and a sparefuse controller which is controlled by the redundancy enable signal andconfigured to output a selection control signal that selects at leastone of the redundant selector and the spare redundant selector inaccordance with an internal fuse option during a normal mode or apredetermined address signal corresponding to the redundant selectionsignal during a test mode.

In accordance with still another embodiment of the present invention, aredundancy circuit of a semiconductor memory device comprises: a fuseset controller for outputting a redundancy enable signal, such fuse setcontroller enabled according to applied address signals; a spare fuseunit for outputting a plurality of fuse-out signals of predeterminedlogic levels corresponding to an internal spare fuse option; a redundantselector controlled by a selection control signal applied from anexterior source configured to output the redundancy enable signal as anormal selection control signal; and a multiplexer for enabling aredundant selection signal or a spare redundant selection signal inaccordance with the plurality of fuse-out signals.

BRIEF DESCRIPTION OF THE DRAWINGS

The above description and other features of the present invention willbecome apparent from the following description of embodiments taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram setting forth a prior art redundancy circuit;

FIG. 2 is a timing diagram representing operation of the prior artredundancy circuit;

FIG. 3 is a block diagram setting forth a redundancy circuit of asemiconductor memory device in accordance with a first embodiment of thepresent invention;

FIG. 4 is a block diagram setting forth a configuration of a spare fusecontroller in accordance with an embodiment of the present invention;

FIG. 5 is a circuit diagram setting forth a spare fuse unit of theredundant circuit in accordance with an embodiment of the presentinvention;

FIG. 6 is a block diagram setting forth a detail configuration of aselecting controller in accordance with an embodiment of the presentinvention;

FIG. 7 is a circuit diagram setting forth a normal selector of theselecting controller in accordance with an embodiment of the presentinvention;

FIG. 8 is a circuit diagram setting forth a test mode selector of theselecting controller in accordance with an embodiment of the presentinvention;

FIG. 9 is a circuit diagram setting forth a signal coupler of theselecting controller in accordance with an embodiment of the presentinvention;

FIG. 10 is a timing diagram of the redundancy circuit in accordance withan embodiment of the present invention when the spare fuse unit isconnected;

FIG. 11 is a timing diagram of the redundancy circuit in accordance withan embodiment of the present invention when the spare fuse isdisconnected;

FIG. 12 is a block diagram setting forth a redundancy circuit inaccordance with a second embodiment of the present invention; and

FIG. 13 is a circuit diagram setting forth a detail configuration of amultiplexer in accordance with the second embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully with reference tothe accompanying drawings, in which exemplary embodiments of theinvention are shown.

FIG. 3 is a block diagram setting forth a redundancy circuit inaccordance with a first embodiment of the present invention.

Referring to FIG. 3, the inventive redundancy circuit includes a fuseset controller 310, a spare fuse controller 320, a redundant selector330, and a spare redundant selector 340.

In one embodiment of the present invention, the fuse set controller 310of the present invention has the same constitution with that of theprior art redundancy circuit. The fuse set controller 310 outputsredundancy enable signals REDEN<0:3> of logic high levels according to apredetermined combination of applied address signals ADDRESS.

The spare fuse controller 320 enables redundant selection controlsignals RED_SELECT<0:3> or a spare redundant selection control signalSPARE RED_SELECT according to a fuse option in a normal mode. Inaddition, in a test mode, the spare fuse controller 320 may enable theredundant selection control signals RED_SELECT<0:3> or the spareredundant selection control signals SPARE RED_SELECT according topredetermined command signals corresponding to redundant selectionsignal RED_SEL<0:3> enabled at the test mode, e.g., predeterminedaddress signals ADDRESS<0:3>.

The redundant selector 330 performs a logic operation to the redundantselection control signals RED_SELECT<0:3> and a selection control signalSEL_CTRL so as to output redundant selection signals RED_SEL<0:3> forselecting a redundancy address corresponding thereto.

The spare redundant selector 340 performs a logic operation to the spareredundant selection control signals SPARE RED_SELECT and the selectioncontrol signal SEL_CTRL so as to output a spare redundant selectionsignal SPARE REDUNDANT SEL for selecting a spare redundancy addresscorresponding thereto.

FIG. 4 is a block diagram setting forth a configuration of the sparefuse controller 320 in accordance with the first embodiment of thepresent invention.

Referring to FIG. 4, the spare fuse controller 320 includes a spare fuseunit 410 and a selecting controller 420. In accordance with anembodiment of the present invention, the spare fuse unit 410 isinitialized by means of a fuse control signal FUSE_CTRL and the sparefuse unit 410 may output fuse-out signals FUSE_OUT<0:3> havingpredetermined logic levels corresponding to a connection or adisconnection of the spare fuse unit 410.

The selecting controller 420 enables the redundant selection controlsignal RED_SELECT<0:3> or the spare redundant selection control signalSPARE RED_SELECT according to logic levels of the fuse-out signalsFUSE_OUT<0:3> in a normal mode. Additionally, the selecting controller420 may enable the redundant selection control signals RED_SELECT<0:3>or the spare redundant selection control signals SPARE RED_SELECTaccording to predetermined command signals corresponding to redundantselection signal RED_SEL<0:3> enabled at the test mode, e.g.,predetermined address signals ADDRESS<0:3>.

FIG. 5 is a circuit diagram setting forth the spare fuse unit 410 of theredundant circuit in accordance with the first embodiment of the presentinvention.

Referring to FIG. 5, the spare fuse unit 410 includes a first spare fuseoutput unit 510, a second spare fuse output unit 520, a decoder enablesignal generator 530, and a decoder 540. The spare fuse unit 410 outputsthe fuse-out signals FUSE_OUT<0:3> having predetermined logic levelscorresponding to a connection or a disconnection state of a first fuseFUSE1 and a second fuse FUSE2.

In one embodiment of the present invention, the first spare fuse outputunit 510 is provided with a first fuse 511 disposed between a powervoltage VDD and a first common node COM1, a first NMOS transistor 512controlled by the fuse control signal FUSE_CTRL of which ends areconnected to the first common node COM1 and a ground voltage VSS, afirst inverter 513 for inverting a logic level of the first common nodeCOM1, and a second NMOS transistor 514 controlled by the output of thefirst inverter 513 of which ends are connected to the first common nodeCOM1 and the ground voltage VSS. When the fuse control signal FUSE_CTRLof logic high level is applied under the condition that first fuse 511is disconnected, the logic level of the first common node COM1 becomeslow. On the contrary, when the fuse control signal FUSE_CTRL of a logichigh level is applied under the condition that first fuse 511 isconnected, the logic level of the first common node COM1 becomes high.

The second spare fuse output unit 520 is provided with a second fuse 521disposed between the power voltage VDD and a second common node COM2, athird NMOS transistor 522 controlled by the fuse control signalFUSE_CTRL of which ends are connected to the second common node COM2 andthe ground voltage VSS, a second inverter 523 for inverting a logiclevel of the second common node COM2, and a fourth NMOS transistor 524controlled by the output of the second inverter 523 of which ends areconnected to the second common node COM2 and the ground voltage VSS.

The decoder enable signal generator 530 has the same constitution withthat of the first spare fuse output unit 510 so that further descriptionfor its constitution will be omitted herein. In one embodiment of thepresent invention, the decoder enable signal generator 530 is requiredfor cutting off the output of decoder 540, when the spare fuse unit isnot used.

The decoder 540 is enabled after being controlled by a decoder enablesignal DECODER_ENABLE outputted from the decoder enable signal generator530. Thereafter, the decoder 540 outputs a first to a fourth fuse-outsignals FUSE_OUT<0:3> by decoding the output signals of the first andthe second spare fuse output units 510 and 520, which correspond to theconnection states of the first and the second spare fuses 511 and 521.

According to one embodiment of the present invention, though it is notshown in the drawings, each of the first and the second spare fuseoutput units 510 and 520 and the decoder enable signal generator 530 maybe provided with a fuse interconnected between a ground voltage VSS anda common node, an NMOS transistor controlled by the fuse control signalFUSE_CTRL which is interconnected between the common node and the powervoltage VDD, an inverter for inverting a logic level of the common node,and another NMOS transistor controlled by the output of the inverterwhich is interconnected between the common node and the power voltageVDD.

FIG. 6 is a block diagram setting forth a configuration of the selectingcontroller 420 in accordance with the first embodiment of the presentinvention.

Although the selecting controller 420 is not limited to the scope of thedescription, it may be configured with a normal selector 610.

In one embodiment of the present invention, the normal selector 610enables normal selection control signals NS<0:3> or a spare selectioncontrol signal SS according to logic levels of the fuse-out signalsFUSE_OUT<0:3>, in response to the redundancy enable signals REDEN<0:3>applied during a normal mode, wherein the redundancy test signalRED_TEST is in a logic low level. Herein, it is possible to make use ofthe normal selection control signal NS<0:3> and the spare selectioncontrol signal SS as the redundant selection control signalRED_SELECT<0:3> and the spare redundant selection control signal SPARERED_SELECT, respectively.

In an alternative embodiment of the present invention, the selectingcontroller 420 may comprise a normal selector 610, a test mode selector620, and a signal coupler 630 as depicted in FIG. 6.

The normal selector 610 enables the normal selection control signalsNS<0:3> or the spare selection control signal SS in the normal mode,wherein the redundancy test signal RED_TEST is in a logic low level.According to one embodiment of the present invention, the spareredundant selection signal SPARE RED_SELECT may replace any number ofthe first to the fourth redundant selection signals of RED_SEL<0:3>according to the logic levels of the fuse-out signals FUSE_OUT<0:3>. Inresponse to the applied redundancy enable signals REDEN<0:3>, the firstto the fourth redundant selection control signals RED_SELECT<0:3> or thespare redundant selection signal SPARE RED_SELECT may be enabled.

In one embodiment of the present invention, during the test mode wherethe redundancy test signal RED_TEST is in a logic high level, the normalselection control signals NS<0:3> and the spare selection control signalSS are set to a logic low level so that the normal selector 610 is notin operation.

The test mode selector 620 enables test mode selection control signalTNS<0:3> or a test mode spare selection control signal TSS, enabled atthe test mode where the redundancy test signal RED_TEST is in a logichigh level.

In accordance with an embodiment of the present invention, the signalcoupler 630 performs a logic OR operation to the normal selectioncontrol signals NS<0:3> and the test mode selection control signalsTNS<0:3>, as well as a logic OR operation to the spare selection controlsignal SS and the test mode spare selection control signal TSS.

FIG. 7 is a circuit diagram setting forth the normal selector 610 of theselecting controller 420 in accordance with an embodiment of the presentinvention.

Referring to FIG. 7, the normal selector 610 comprises a first to aninth inverters 711 to 719 and a first to a ninth NAND gates 721 to 729.Herein, the first inverter 711 is used for inverting a first fuse-outsignal FUSE_OUT<0> and the second inverter 712 is used for inverting asecond fuse-out signal FUSE_OUT<1>. Likewise, the third and the fourthinverters 713 and 714 invert a third fuse-out signal FUSE_OUT<2> and afourth fuse-out signal FUSE_OUT<3> respectively. The fifth inverter 715inverts the redundancy test signal RED_TEST.

In accordance with an embodiment of the present invention, the firstNAND gate 721 performs a logic NAND operation to the output of the firstinverter 711, a first redundancy enable signal REDEN<0>, and the outputof the fifth inverter 715. The second NAND gate 722 performs a logicNAND operation to the output of the second inverter 712, a secondredundancy enable signal REDEN<1>, and the output of the fifth inverter715. Likewise, the third NAND gate 723 performs a logic NAND operationto the output of the third inverter 713, a third redundancy enablesignal REDEN<2>, and the output of the fifth inverter 715. The fourthNAND gate 724 performs a logic NAND operation to the output of thefourth inverter 714, a fourth redundancy enable signal REDEN<3>, and theoutput of the fifth inverter 715.

The fifth NAND gate 725 performs a logic NAND operation to the firstfuse-out signal FUSE_OUT<0>, the first redundancy enable signalREDEN<0>, and the output of the fifth inverter 715. Likewise, the sixthNAND gate 726 performs a logic NAND operation to the second fuse-outsignal FUSE_OUT<1>, the second redundancy enable signal REDEN<1>, andthe output of the fifth inverter 715. The seventh NAND gate 727 performsa logic NAND operation to the third fuse-out signal FUSE_OUT<2>, thethird redundancy enable signal REDEN<2>, and the output of the fifthinverter 715. The eighth NAND gate 728 performs a logic NAND operationto the fourth fuse-out signal FUSE_OUT<3>, the fourth redundancy enablesignal REDEN<3>, and the output of the fifth inverter 715.

In accordance with an embodiment of the present invention, the ninthNAND gate 729 plays a role in performing a logic NANAD operation to theoutputs of the fifth to the eighth NAND gates 725, 726, 727, and 728.

In one embodiment of the present invention, a sixth to a ninth inverters716, 717, 718, and 719 are used for inverting only the output of thefirst to the fourth NAND gates 721, 722, 723, and 724. It should beappreciated that the first NAND gate 721 and the sixth inverter 716 maybe substituted by one AND gate. In accordance with an embodiment of thepresent invention, in the test mode where the redundancy test signalRED_TEST is in a logic high level, the normal selection control signalNS<0:3> and the spare selection control signal SS are set to a logic lowlevel, wherein the normal selector 610 is not in operation.

FIG. 8 is a circuit diagram setting forth the test mode selector 620 ofthe selecting controller 420 in accordance with the first embodiment ofthe present invention.

Referring to FIG. 8, the test mode selector 620 performs logic operationto the address signals ADDRESS<0:3>, the address signal ADDRESS<4>, andthe redundancy test signal RED_TEST, to thereby enable the redundantselection control signals RED_SELECT<0:3> or the spare redundantselection control signal SPARE RED_SELECT.

FIG. 9 is a circuit diagram setting forth the signal coupler 630 of theselecting controller 420 in accordance with an embodiment of the presentinvention.

Referring to FIG. 9, the signal coupler 630 comprises a first to afourth NOR gates for performing a logic NOR operation to the first tothe fourth normal selection control signals NS<0:3> and the first to thefourth test mode selection control signals TNS<0:3>, and a fifth NORgate 915 for performing a logic NOR operation to the spare selectioncontrol signal SS and the test mode spare selection control signal TSS.

In accordance with an embodiment of the present invention, a first to afifth inverters 921 to 925 are used for inverting only the outputs ofthe first to the fifth NOR gates 911 to 915. It should be appreciatedthat the first NOR gate 911 and the first inverter 921 may besubstituted by one OR gate, the second NOR gate 921 and the secondinverter 922 may be substituted by one OR gate, etc.

FIG. 10 is a timing diagram of the redundancy circuit in accordance withan embodiment of the present invention when the spare fuse unit isconnected, wherein the fuse-out signals FUSE_OUT<0:3> are set to a logiclow level.

First Period (T1-T2)

The first period is a normal operation period that the redundancy testsignal RED_TEST is in a logic low level, and thus the first and thesecond fuses 511 and 512 are connected to their own parts as shown inFIG. 5.

The fuse set controller 310 outputs the redundancy enable signalREDEN<0:3> by combining the address signals ADDRESS applied from anexterior source. Referring to FIG. 10, for instance, though it is shownthat the first redundancy enable signal REDEN<0> turns to a logic highlevel, the first to the fourth redundancy enable signals<0:3> may beenabled, i.e., set to a logic high level, respectively.

In one embodiment of the present invention, the spare fuse unit 410 mayoutput the first fuse-out signal FUSE_OUT<0> of a logic low level underthe condition that the first fuse 511 and the second fuse 512 areconnected to their own parts. At this time, the normal selector 610 ofthe selecting controller 420 is controlled by the first redundancyenable signal REDEN<0> which is set to a logic high level. Thus, thenormal selector 610 enables the first normal selection control signalNS<0> by setting the control signal to a logic high level. On thecontrary, since the redundancy test signal RED_TEST keeps a logic lowlevel, the test mode selector 620 maintains the test mode selectioncontrol signals TNS<0:3> and the test mode spare selection controlsignal TSS in a logic low level so that the test mode selector 620 doesnot operate. Furthermore, because the first normal selection controlsignal NS<0> is set to a logic high level, the signal coupler 630 setsthe first redundant selection control signal RED_SELECT<0> to a logichigh level, and subsequently the redundant selector 330 controlled bythe selection control signal SEL_CTRL enables (i.e., sets to a logichigh level) the first redundant selection signal RED_SEL<0>.

2) Second Period (T2-T3)

The second period is the test mode period that the redundancy testsignal RED_TEST is in a logic high level.

In one embodiment of the present invention, the test mode selector 620sets the first test mode selection control signal TNS<0> to a logic highlevel and the signal coupler 630 sets the first redundant selectioncontrol signal RED_SELECT<0> to a logic high level. Furthermore, theredundant selector 330 controlled by the selection control signalSEL_CTRL enables (i.e., sets to a logic high level) the first redundantselection signal RED_SEL<0>. In accordance with an embodiment of thepresent invention, the output of the normal selector 610 has no effecton the signal coupler 630 because the redundancy test signal RED_TEST ofa logic high level sets the spare selection control signal SS and thenormal selection control signals NS<0:3> outputted from the normalselector 610 to a logic low level.

3) Third period (after T3)

The third period is the test mode period that the redundancy test signalRED_TEST and the second test mode selection control signal TNS<1> are ina logic high level.

In one embodiment of the present invention, the operational mechanismfor the third period is the same as that for the second period. However,there is a difference in that the second redundant selection signalRED_SEL<1> is set to a logic high level instead of the first redundantselection signal RED_SEL<0> being set to a logic high level, because thesecond test mode selection control signal TNS<1> is set to a logic highlevel instead of the first test mode selection control signal TNS<0>being set to a logic high level, shown in the second period.

FIG. 11 is a timing diagram of the redundancy circuit in accordance withthe first embodiment of the present invention, wherein the spare fuse isdisconnected, and the first fuse-out signal FUSE_OUT<0> is in a logichigh level.

1) First Period (T1-T2)

The first period is a normal operation period that the redundancy testsignal RED_TEST is in a logic low level and the first fuse-out signalFUSE_OUT<0> is in a logic high level.

The fuse set controller 310 outputs the redundancy enable signalREDEN<0:3> by combining the address signals ADDRESS applied from anexterior source. For example, provided that the first redundancy enablesignal REDEN<0> is set to a logic high level, the normal selector 610 ofthe selecting controller 420 is controlled by the first redundancyenable signal REDEN<0> which is set to a logic high level, therebysetting the spare selection control signal SS to a logic high level.Since the redundancy test signal RED_TEST is kept at a logic low level,the test mode selector 620 maintains the test mode selection controlsignal TNS<0:3> and the test mode spare selection control signal TSS ina logic low level so that the test mode selector 620 does not operate.

Furthermore, because the spare selection control signal SS is set to alogic high level, the signal coupler 630 sets the spare redundantselection control signal SPARE RED_SELECT to a logic high level. Inaddition, the spare redundant selector 340 controlled by the selectioncontrol signal SEL_CTRL enables (i.e., sets to a high logic level) thespare redundant selection signal SPARE REDUNDANT SEL.

2) Second Period (T2-T3) and Third Period (after T3)

Since these periods are in the test mode period where the redundancytest signal RED_TEST is in a logic high level, the operational mechanismis same to that of the descriptions in FIG. 10, and furtherillustrations will be omitted herein.

FIG. 12 is a block diagram setting forth a redundancy circuit inaccordance with a second embodiment of the present invention.

Referring to FIG. 12, the redundancy controller of the second embodimentcomprises a fuse set controller 1210, a spare fuse unit 1220, aredundant selector 1230, and a multiplexer 1240.

In one embodiment of the present invention, the fuse set controller 1210has the same constitution with that of the fuse set controller of FIG.1, and outputs the redundancy enable signals REDEN<0:3> which is enabledby a predetermined combination of applied address signals ADDRESS.

In one embodiment of the present invention, the spare fuse unit 1220 hasthe same configuration with that of the spare fuse unit of FIG. 5, andoutputs the fuse-out signals FUSE_OUT<0:3> of which logic levels aredetermined according to the connection state of the first and the secondspare fuses FUSE1 and FUSE2.

The redundant selector 1230 which is controlled by the selection controlsignal SEL_CTRL outputs the enabled redundancy enable signals REDEN<0:3>as the normal selection control signals NS<0:3>.

In accordance with an embodiment of the present invention, themultiplexer 1240 enables the first to the fourth redundant selectionsignals RED_SEL<0:3> normally under the condition that the first and thesecond spare fuses FUSE1 and FUSE2 are connected to their own parts.However, when a predetermined signal having a logic level different fromthe other signals, i.e., among the first to the fourth fuse-out signalsFUSE_OUT<0:3>, the multiplexer 1240 enables the spare redundantselection signal SPARE REDUNDANT SEL and the redundant selection signalsexcept a redundant selection signal corresponding to the predeterminedsignal having the different logic level. For example, if the firstfuse-out signal FUSE_OUT<0> has a logic level different from that of thesecond to the fourth fuse-out signals FUSE<1:3>, the multiplexer 1240enables the spare redundant selection signal SPARE REDUNDANT_SEL and thesecond to the fourth redundant selection signals RED_SEL<1:3> except thefirst redundant selection signal RED_SEL<0> corresponding to the firstfuse-out signal FUSE_OUT<0>.

FIG. 13 is a circuit diagram setting forth a configuration of themultiplexer 1240 of FIG. 12 in accordance with the second embodiment ofthe present invention.

Since a logical relation between the input/output signals in themultiplexer 1240 is obvious for those skilled in the art, detaildescriptions will be abbreviated herein.

It should be appreciated that a first NAND gate ND1 and a secondinverter IV2 may be substituted by one AND gate, and a fifth to a ninthNAND gates may be replaced by one AND gate.

In one embodiment of the present invention, it is possible to reuse thefuse, wherein it is more beneficial to a circuit design of asemiconductor memory device. In addition, since a defective redundancyarea can be replaced in virtue of the fuse option, it is possible toalso enhance productivity.

While the present invention has been described with respect to theparticular embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

1. A redundancy circuit in a semiconductor memory device comprising: afuse set controller configured to output a redundancy enable signalbased on an input of applied address signals; a redundant selector; aspare redundant selector; and a spare fuse controller configured to becontrolled by the redundancy enable signal and to output a selectioncontrol signal that selects at least one of the redundant selector andthe spare redundant selector.
 2. The redundancy circuit of claim 1,wherein the selection control signal is in accordance with an internalfuse option.
 3. The redundancy circuit of claim 1, wherein the sparefuse controller comprises: a spare fuse unit configured to beinitialized by a fuse control signal applied from an exterior source,and to output a fuse-out signal having a predetermined logic levelcorresponding to an internal fuse option; and a selecting controllerconfigured to output the selection control signal in accordance with thefuse-out signal generated in response to the redundancy enable signal.4. The redundancy circuit of claim 3, wherein the spare fuse unitcomprises: a plurality of spare fuse output units controlled by the fusecontrol signal, and are configured to output signals of predeterminedlogic levels corresponding to the internal fuse option; a decoderconfigured to output a plurality of fuse-out signals determined bydecoding the output signals of the plurality of spare fuse output units;and a decoder enable signal generator configured to be controlled by thefuse control signal and to enable the decoder.
 5. The redundancy circuitof claim 4, wherein the selecting controller outputs a redundantselection control signal used to enable the redundant selector, whereinthe redundant selection control signal is based on the plurality offuse-out signals.
 6. The redundancy circuit of claim 4, wherein theselecting controller outputs a spare redundant selection control signalused to enable a spare redundant selector, wherein the spare redundantselection control signal is based on the plurality of fuse-out signals.7. The redundancy circuit of claim 5, wherein the redundant selectorperforms a logic operation to the redundant selection control signal andthe selection control signal applied from an exterior source so as tooutput a redundant selection control signal, and the spare redundantselector performs a logic operation to the spare redundant selectioncontrol signal and the selection control signal so as to output a spareredundant selection control signal.